Observations on the idioblasts of Dieffenbachia.

The toxicity of the Arum genus, especially the Dieffenbachia, has long been a topic of controversy. Some believe that the injury inflicted is primarily mechanical, the result of needle like crystals of calcium oxalate (raphides) found in the stems and leaves. Others cite evidence supporting the existence of enzymatic and allergic injury. This paper describes a hitherto neglected third factor, specialized cells which can forcibly shoot the raphides and which may be necessary for the toxic effect since raphide containing plants devoid of these cells are not toxic. The effects of physical and chemical factors on the behavior of these cells are described.